Foam Insulation Underside Of Roof

The osb got wet and rotted.

Foam insulation underside of roof.

This can happen when the roof becomes damaged on the outside and water gets into the space between the spray foam and the underside of the slates. To get the best performance out of spray foam insulation you must cover the roof rafters and surrounding areas as thoroughly as possible. If yes consider doing a cold roof which uses baffles to leave an inch of air flow between the seal of to the inside of the house and the roof sheething like a roof under a roof. It will help you to eliminate problems that may come when the house becomes extremely cold in the winter and terribly hot in the summer.

This can cause condensation due to the temperature difference between in this space compared to the rest of the loft room. The authors of the first paper cited a study in south carolina where the relative humidity in the attic was way too high in summer 80 to. Moving the air control layer and thermal control layer to the underside of the roof deck has significant advantages in cases where the hvac system is located in the attic. Some houses with open cell spray foam installed on the underside of the osb roof sheathing have had moisture problems.

But where does the moisture come from. You may also need to inspect the foam at intervals to see whether any shrinkage has. This illustration shows a sloped roof with cavity spray foam insulation sprayed on the underside of the roof deck and covered with sprayed on thermal or ignition barrier coating. In addition to installing the foam board on the underside of the roof deck you can attach it to the bottom edges of the rafters in the same manner you would hang drywall.

The movement of air into indirect conditioning of an unvented attic is a slow gradual process that will not be noticeable by occupants and typically will not put any strain on the hvac system. But spray foam insulation used at the underside of the roof deck would need to be covered by a thermal barrier and intumescent coatings are commonly used.